Fabric softeners are widely used by home consumers and commercial laundries to provide softness, surface smoothness, good draping qualities, fluffiness and antistatic properties while avoiding surface greasiness or excessive build-up on the fabric. Although fabric softener technology is well known, the exact softening mechanism is not known. One commonly accepted mechanism relates softness to the lubricity of the adsorbed softener on the cloth and the consequent reduction of friction between the fabric fibers.
Fabric softener compositions that can be added to the rinse water when washing household laundry normally contain, as active substance, a water-insoluble quaternary ammonium compound. Commercially available fabric softener compositions are based on aqueous dispersions of water-insoluble quaternary compounds. Recently, there has been increasing interest in biodegradable active substances. Such substances include, for example, esters of quaternary ammonium compounds, so-called “esterquats,” which have at least one long-chain hydrophobic alkyl or alkenyl group interrupted by carboxyl groups.
Active substances in fabric softener compositions that impart a good soft handle to the treated textile generally have the disadvantage that they may lower the water absorbency and wickability of the textile fabric. This is troublesome in the use of 100% cotton items, such as towels and diapers, where softness and water absorbency properties are both desired. The problem is generally exacerbated in more hydrophobic synthetic fibers, such as polyester, polypropylene and nylon and blends thereof with other synthetic and natural fibers. The problem may be so severe that many garments made from high performance fabrics where the ability to rapidly wick water from the skin and dry quickly actually include warnings against using any fabric softener during the laundering process because the use of the fabric softener may destroy the water-absorbency, rewettability and wickability properties of the fabric—properties key to their performance. The disadvantage of reduced water absorbency is often highly pronounced in the case of certain active substances, such as the fatty acid quats.
Others have addressed this trade-off in softness and water-absorbency properties. For example, U.S. Pat. No. 6,358,913 discloses a fabric softener composition containing:    (a) as an active substance, a quaternary ammonium compound of the formula:      where R is the aliphatic radical of tallow fatty acid, in particular a mono- or polyunsaturated aliphatic C17 radical; and    (b) a nitrogen-free polydiorganosiloxane having terminal silicon-bonded hydroxyl groups.
However, there is still a need for additional fabric softener compositions that improve the water-absorbency, rewettability and wickability properties of the treated textiles without impairing the other desirable properties of the treated textiles provided by use of the compositions, such as softness and static properties. The present invention is directed to this, as well as other important ends.